Exposure to sunlight and other sources of ultraviolet (UV) radiation is known to cause degradation of a wide variety of materials, especially polymeric materials. For example, polymeric materials such as plastics often discolor, lose gloss and/or become brittle as a result of prolonged exposure to UV light due primarily to a reduction in the molecular weight of the polymer. Accordingly, a large body of art has been developed directed towards materials such as UV light absorbers and stabilizers, which are capable of inhibiting such degradation in polymeric articles.
U.S. Pat. No. 4,670,491 discloses the use of a C12 to C20 alkyl esters of 3,5-tertbutyl-4-hydroxybenzoic acid to stabilize a titanium dioxide pigmented olefin composition. U.S. Pat. No. 5,240,977 discloses the use of a 3,5-disubstituted tert-butyl-4-hydroxybenzate with a triazine based hindered amine light stabilizer (HALS) in a pigmented polyolefin composition. U.S. Pat. No. 3,206,431 discloses the use of alkyl esters of 3,5-di-tert-butyl-4-hydroxybenzoic acid as light stabilizers for polyolefins in combination with a hindered phenol antioxidant. U.S. Pat. Nos. 3,681,431 and 3,285,855 disclose the use of n-octadecyl 3,5-di-tert-butyl-4-hydroxybenzoate as an antioxidant for polyolefins. British Pat. No. 1,336,931 teaches the use of aryl esters of 3,5-di-tert-butyl-4-hydroxybenzoic acid as light stabilizers for polyolefins in combination with a benzophenone and a peroxide decomposer. U.S. Pat. No. 3,502,613 teaches a synergistic combination of an aryl ester of 3,5-di-tert-butyl-4-hydroxybenzoic acid, a chlorobenzotriazole, a phenolic antioxidant, and a thiodipropionate ester as a light stabilizer for polypropylene. U.S. Pat. No. 4,237,042 discloses a light stabilizer composition for polyolefins comprising n-hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate and a dialkyl pentaerythrityl diphosphite.
None of the above documents disclose the use of a hindered hydroxybenzoate compound with an ortho-hydroxy triazine UV absorber either with or without a hindered amine compound.